This invention relates generally to medical apparatus and, more particularly, to a new and improved catheter tip design enabling very accurate and reliable intracardiac recording of and delivery of energy to the atrioventricular junction conductive tissue.
An electrode catheter technique has been developed to record electrical activation of the His bundle (atrioventricular or A-V bundle) and bundle branches via a pervenous femoral approach. With this technique an electrode catheter is inserted percutaneously via a femoral vein and advanced under fluoroscopic control through the inferior vena cava to the right atrium and across the tricuspid (right atrioventricular) valve into the right ventricle. The catheter tip is gradually withdrawn from the right ventricle into the right atrium and scraped along the interatrial septum until electrical activity of the His bundle is received. The His bundle activity is recorded as a rapid biphasic or triphasic potential sandwiched between atrial and ventricular activations. The tip of these prior art electrode catheters is either straight or gently curved in a single plane.
However, morphologically, the central longitudinal axis of the inferior vena cava is generally parallel to the interatrial septum. Since the bundle of His begins at the A-V node, laterally relative the inferior vena cava, the use of a straight or planar catheter tips prevents placing the tip in contact with the bundle of His. As a result, the catheter tip merely floats close to the desired location.
More specifically, since the catheter tip is not passively contacting the His bundle, it slides back and forth against the tricuspid valve, resulting in changes in the morphology and the amplitude of the detected electrical potential of the His bundle. It is believed that this is due to catheter tip motion, to and fro, across the valve and away from the septal leaflet. Because of this motion, the degree of separation between the endocardial surface of the His bundle and the recording electrode is never known and may vary from beat-to-beat or with respiratory movements. Variations in contact or the space between the electrode and the endocardium results in variations in the amplitude and morphology of the His bundle potential.
In addition, since the catheter tip is not fixed to the endocardial surface, a constant relationship between the electrode and the precise point on the A-V junction from which the electrical activity is being recorded is not maintained. As a result, the point upon the A-V junction from which electrical activity is being recorded may vary from beat-to-beat or with cardiac or respiratory motion.
During approximately the last five years, the His bundle recording technique has also been utilized for therapeutic purposes to ablate the His bundle by delivery of various types of energy, especially "DC shock" (the application of direct current voltage). This technique is described by J. Gallagher, et al. in "Catheter Technique For Closed-Chest Ablation Of The Atrioventricular Conduction System," New England Journal of Medicine, Vol. 306, No. 4, Jan. 28, 1982, pp. 194-200. This approach entails the recording of potentials by a standard His bundle recording technique, utilizing an electrode catheter and delivery of energy through the same catheter system. However, a moving and floating catheter tip does not maintain a good contact with the endocardial surface and thus the site at which the energy is being delivered. This may result in requiring a greater amount of energy to compensate for this method of delivery.
Hence, those concerned with the development and use of internal organ monitoring and electrostimulation systems in the medical field, e.g., intracardiac systems, have long recognized the need for improved catheters and electrode systems which enable a more accurate and reliable placement and contact of the catheter at the desired internal location. The present invention fulfills all of these needs.